Under the 3GPP standards, a NodeB (or an eNB in LTE (i.e. Long Term Evolution)) is the home base station part via which mobile devices connect to the core network and which defines a cell of the network. Home base stations or home base station parts (HNB) provide short range 3G radiofrequency (RF) coverage, and are sometimes referred to as a femto access point (FAP). Where the home base station is operating in accordance with the LTE standards, the HNB is commonly referred to as an HeNB. Some base stations, sometimes referred to as HNB/HeNB, can operate in accordance with both the 3G and LTE standards, and therefore define a dual mode femtocell. The HNB/HeNB base station may also sometimes be referred to as a dual mode femto access point (FAP) or dual FAP.
The HNB or HeNB provides radio coverage (for example, 3G, 4G and/or WiMAX) within the home, small or medium enterprise, shopping malls, etc. and typically connects to the core network via a suitable residential gateway RG and public or corporate broadband (BB) access network (for example via an ADSL link to the Internet) to provide the HNB or HeNB with a backhaul communication line or link with an available bandwidth. The HNB or HeNB is given an IP address by the local network to which it is connected, and the HNB or HeNB provides this IP address to the mobile telephone operator network so that it can reserve appropriate resources for the HNB or HeNB through the broadband access network.
During operation in a normal operation mode or normal state, the HNB or HeNB enables users of a User Equipment (UE) to communicate with other such users via one of a number of the base stations (eNodeB, eNB) and a core network.
In a connected or active state or mode, a UE is registered with the network and has an RRC (Radio Resource Control) connection with a base station, so that the network can identify which cell the UE belongs to and can transmit data to and receive data from the UE. In LTE, in the active state or mode, the Handover procedure allows UEs to have service continuity while moving within the Intra LTE system (Intra RAT and Inter Frequency) and towards other RATS (Radio Access Technologies).
A UE also has a power conservation or idle state or mode in which, typically, the UE is not transmitting or receiving data, and no context about the UE is stored by the base station. In the idle state, the location of the UE is known only (to the MME (Mobility Management Entity) in 3GPP) at the granularity of a Tracking Area (TA) comprising a cluster or group of base station cells. When in the idle state, a UE selects and reselects cells according to the parameters broadcast by the base station in the BCH (Broadcast Channel), with a frequency given by a Tracking Area Update Timer Value, and the base station is not aware of the cell selections/reselections made by the UE.
During the normal operation mode, the HNB or HeNB usually periodically broadcasts a downlink transmission comprising reference signals and system information, for instance both the Pilot and the Broadcast Channels, to signal its presence to UEs.
In dual mode cells, both the baseband and the radiofrequency processing hardware blocks of the HeNB are independent from the baseband and the radiofrequency processing hardware blocks of the HNB.
To be able to admit new UE (sometimes referred to as radio bearers), a base station (for instance an HeNB of a dual FAP) should have aggregate communication traffic which does not exceed the available backhaul bandwidth (also referred to as Transport Network Layer (TNL) resources) in the uplink and/or downlink directions. If the aggregate traffic of the base station might exceed the available backhaul bandwidth in the uplink and/or downlink directions if a UE is admitted, then the UE or bearer might need to be handed over or redirected to a macro cell even when operation in the dual FAP is preferred, for example to reduce costs to an end user who is a member of a closed subscriber group associated with the base station. Furthermore, since a femto cell operator may not also manage the macro cell network, the handing over of the UE or bearer to a macro cell may result in a loss in revenue to the femto cell operator and an increase costs to the end user.